1. Field of the Invention
The present invention relates to an optical tomographic imaging apparatus, and in particular, to an S/N enhancement technique in optical coherence tomography (OCT) measurement which is not restricted by the light intensity of a light beam irradiated on a subject to be examined.
2. Description of the Related Art
Conventionally, there are known optical tomographic imaging apparatuses utilizing optical coherence tomography (OCT) measurement as a method of acquiring a tomographic image without dissecting a measurement subject such as living tissue.
OCT measurement is an optical interferometric measurement method in which a light beam emitted from a light source is divided into two light beams, namely, a measurement light beam and a reference light beam, and which utilizes the fact that optical interference is only detected when respective optical path lengths of the measurement light beam and the reference light beam match each other within the range of a coherence length of the light source.
For example, an optical tomographic imaging apparatus is known that is an application to SS-OCT (swept source OCT) of the concept of an S/N enhancement technique using light amplification in TD-OCT (time-domain OCT), wherein by optically amplifying a reflected light beam reflected off of a measured section and then causing the reflected light beam to interfere with a reference light beam, and by measuring the intensity of the interference light beam, S/N can be enhanced while maintaining signal light intensity is maintained at a level where the safety of the measured section can be secured (for example refer to Jun Zhang et. al. “Coherent amplified optical coherence tomography”, Proc. of SPIE-OSA Biomedical Optics, SPIE Vol. 6627, 662718 (2007)).